Peoples

In the Middle Ages “peoples” was not an uncommon word, but later writers grew wary of it because “people” has a collective, plural meaning which seemed to make “peoples” superfluous.

It lived on in the sense of “nations” (“the peoples of the world”) and from this social scientists (anthropologists in particular) derived the extended meaning “ethnic groups” (“the peoples of the upper Amazon Basin”).

However, in ordinary usage “people” is usually understood to be plural, so much so that in the bad old days when dialect humor was popular having a speaker refer to “you peoples” indicated illiteracy.

If you are not referring to national or ethnic groups, it is better to avoid “peoples” and use “people.”

“Behavior” has always referred to patterns of action, including multiple actions, and did not have a separate plural form until social scientists created it.

Unless you are writing in psychology, sociology, anthropology, or a related field, it is better to avoid the use of “behaviors” in your writing.